The invention relates to a method for the supply of lubricant to bearing elements in a hydrodynamic coupling.
Hydrodynamic couplings have previously been disclosed in a plurality of executions for different applications. In order to ensure a reliable function, additional operating circuits, which in their entirety constitute an operating fluid system, are assigned to these in addition to line connections for the purpose of the filling and emptying of the working area. A previously disclosed design of a hydrodynamic coupling comprises at least one primary wheel functioning as a pump wheel and a secondary wheel functioning as a turbine wheel, which together form a toroidal working area, in which the operating fluid is caused to circulate during operation of the hydrodynamic coupling. The resulting circuit is designated as the operating circuit. A circuit which is connected to at least one inlet into the working area and one outlet from the working area, and which serves the purpose of assuring the direct circulation of operating fluid from the working area to the outside and back into the working area during operation of the hydrodynamic coupling, is assigned to the operating circuit for the purpose of cooling the operating fluid. Couplings of this kind are accordingly also referred to as couplings with direct circulation. Cooling devices, for example in the form of heat exchangers or coolers, can be arranged in this circuit, which is executed as a rule as a closed circuit. In addition, at least one supply line is assigned to the operating circuit, and in particular the toroidal working area, which line feeds operating fluid from a container or tank into the operating circuit. This supply line is also designated as a filling line and as such is connected to the operating circuit via the circuit for direct circulation by utilizing this line connection. Also connected to the operating circuit is at least one line for the purpose of emptying. This line is preferably connected to the circuit for direct circulation by making use of a part of the line connections for the direct circulation circuit. Also provided are connecting lines for the supply of lubricant between the container or tank and the individual bearings of the hydrodynamic coupling, which form a so-called lubricant supply system. The lubricant supply system in this case is preferably connected to the filling line. In order to ensure an optimal cooling process or to influence the degree of filling during operation of the hydrodynamic coupling, i.e. by conveying operating fluid from the operating circuit via an external circuit in the form of direct circulation and back to the operating circuit, it is essential for no additional operating fluid to be sucked in in this condition. Means for interrupting the connection between the tank and the operating circuit are provided in the filling line for this purpose, in the simplest case in the form of a valve device with two switching positions. Connection is effected in the direction of flow of the operating fluid from the tank to the operating circuit between the tank and the operating circuit ahead of the means for interrupting the connection between the tank and the operating circuit. A filter device is also provided, which ensures that adequately filtered oil is always available at the bearings in all operating conditions—filling, emptying and direct circulation in normal rating, and in the case of partial filling and possibly in the case of circulation cooling. A major disadvantage of this design, however, is that a proportion of the operating fluid in the form of oil provided for the actual lubrication of the bearings in these conditions finds its way into the operating circuit of the hydrodynamic coupling, which leads to an undesired influence, in particular a change in the level of filling. For the use of hydrodynamic couplings for the purpose of the speed control of a machine, it is then absolutely essential to readjust or set the level of filling via a timed emptying valve. However, this represents a disturbance variable for couplings which utilize direct circulation and which return filling and emptying losses to the operating circuit via the filling line. A balance can only be achieved by resorting to very high timing values for the valve devices. However, this in turn leads to a considerable reduction in the service life of the valve and thus in the availability, i.e. the possible operating life, of the entire system. The cost of the technical control means for such designs is also enormously high.
The object of the invention was thus to develop further a method for the supply of the bearing elements in a hydrodynamic coupling with lubricant in such a way that the level of filling of the hydrodynamic coupling and its mode of operation are influenced not at all or only to an imperceptible extent. The constructive design should accordingly be characterized by a high degree of certainty in ensuring the function of the hydrodynamic coupling, in particular the individual operating phases, and an extended service life for the individual components and a low control and regulation cost.
In accordance with the invention, the supply to the bearing elements of a hydrodynamic coupling comprising at least one primary wheel functioning as a pump wheel and a secondary wheel functioning as a turbine wheel, which together form a toroidal working area for conveying an operating circuit which comes into being during operation, in addition to the supply via the filling line in conditions involving the interruption of the flow of operating fluid between the operating fluid container and the inlet or direct circulation, is effected via a circuit that is already present during operation in order to ensure the conveying or the circulation of operating fluid during operation outside the operating circuit in the form of so-called direct circulation. This means that the supply of lubricant to the bearing elements takes place from the direct circulation. As a rule, this circuit is executed as a closed circuit in this case and connects at least one inlet to an outlet from the hydrodynamic coupling, in particular the toroidal working area. The expressions “inlet” and “outlet” serve a functional purpose in this case and must not necessarily be understood only as constructive features. These are incorporated as a rule in the inner extent of the torus in the wall of the one or more blade wheels and are connected via corresponding channels in the wall of the blade wheels to the external line components, i.e. in lines or channels provided outside the toroidal working area for the purpose of conveying the operating fluid in the direct circulation. Furthermore, at least one filling line is assigned to the hydrodynamic coupling, in particular the toroidal working area, which line is connected to the circuit in the form of direct circulation and is connected via the circuit for direct circulation to at least one inlet into the working area of the hydrodynamic coupling. The circuit for direct circulation constitutes a closed circuit together with the operating circuit. The connection of the filling line to the direct circulation is effected in this case between the outlet and the inlet.
The expression filling line is understood in this case to denote the line which connects the operating fluid source to the direct circulation, i.e. as far as the junction point.
A lubricant supply system is connected to the filling line, which supplies lubricant to at least the bearing elements of the hydrodynamic coupling, and in particular those of the pump wheel and the turbine wheel and the elements that are so arranged as to rotate together with these. The lubricant supply system is supplied, in the event of the disconnection of the filling line from the working area, via the circuit for the direct circulation of operating fluid outside the hydrodynamic coupling, and in particular outside the working area, whereas, in the event of the connection of the filling line to the direct circulation and thus to at least one inlet into the working area via the circuit for direct circulation, the supply of lubricant is provided by utilizing the same source of supply for the operating fluid in each case.
The inventors have recognized that, in the filling and emptying operating modes and in the case of circulation cooling when the operating fluid is being conveyed in the direct circulation from the working area of the hydrodynamic coupling, if necessary via a corresponding cooling device, and back to the working area of the hydrodynamic coupling, the taking of operating fluid from the circuit for the purpose of providing direct circulation from the working area outside the coupling and back into the working area, and the associated losses of operating fluid for the operation of the hydrodynamic coupling and the function in these operating modes, do not play any part for the purposes of bearing lubrication. Lubrication of the bearings is provided in this case on the basis of the energy that is already present in the system in any case for the achievement of the functional mode of the hydrodynamic coupling, i.e. there is no need for an additional device for the supply of lubricant to the bearing elements.
In a further aspect of the invention, the quantity of operating fluid conveyed in the direct circulation and the pressure level which applies there, or a value which characterizes this at least indirectly, are monitored, in conjunction with which monitoring can take place continuously, at intervals or, if necessary, as the need arises, and, where a specified minimum level is not met, a new supply of operating fluid into the operating circuit of the hydrodynamic coupling can be provided by connecting the filling line to the operating circuit. The total operating time of the filling pump can be reduced considerably in this way, because it only needs to be operated when the demand actually exists, which in turn contributes to an increase in the service life of the system as a whole.
According to a further development, means are provided which, during the filling process of the toroidal working area of the hydrodynamic coupling, permit an excess of operating fluid from the filling line into the lubricant system only once a specified pressure has been reached in the system, i.e. in the operating circuit and the direct circulation connected to it. In particular during the start-up procedure of the hydrodynamic coupling, this leads to the lubricant actually provided for the bearing elements finding its way into the operating circuit of the hydrodynamic coupling for as long as the pressure in the direct circulation is lower than the pressure level of the filling pump, which manifests itself in the more rapid filling of the hydrodynamic coupling and an associated improvement in the dynamic system behavior in the drive train.
From the point of view of its design, the hydrodynamic coupling, comprising at least one primary wheel functioning as a pump wheel and a secondary wheel functioning as a turbine wheel, which together form a toroidal working area, in which operating fluid is caused to circulate during operation to form an operating circuit, is executed with an operating fluid system, which includes at least one circuit to convey operating fluid from the working area for the purpose of cooling during operation and its return to the working area in the form of a so-called direct circulation. The operating fluid system also comprises at least one so-called filling line, which connects a source of operating fluid to the operating circuit, i.e. the toroidal working area or an inlet into the toroidal working area. The filling line in this case is preferably connected to the circuit for the direct circulation, in conjunction with which filling takes place using lines belonging to the direct circulation. Here, too, the expression “line” must be understood in a functional sense only, so that channels incorporated into walls are also subsumed under this in addition to pipe-shaped or hose-shaped elements. In order to ensure a stable mode of operation without the need to suck in additional operating fluid during operation, in which a flow of operating fluid from the working area to the working area through an external guiding means outside the toroidal working area is desired for the control of the level of filling and/or for the purpose of cooling, means are provided to assure or interrupt the flow of operating fluid in the filling line between the source of the operating fluid and the inlet or the direct circulation. These means function as means for the connection and disconnection of the filling line to and from the working area, as desired, and in the simplest case comprise a valve device with at least two switching positions. Also connected in accordance with the invention to the filling line is the lubricant supply system, which serves for the supply of the individual bearing elements with lubricant. In order to provide for the supply of the bearing elements with lubricant from the direct circulation, various possibilities exist for the concrete execution and connection of the lubricant system to the filling line and the direct circulation.
According to a first embodiment in accordance with the invention, the lubricant supply system comprises a first connecting line between the filling line and the main lubricant line to the individual bearing elements, in conjunction with which the direction of flow is determined by a valve device, preferably in the form of a nonreturn valve, which blocks the flow in one direction. The connection of the first connecting line is effected in the direction of flow between the source of operating fluid and the working area ahead of the means for providing or interrupting the flow of operating fluid in the filling line and for the connection and/or disconnection of the filling line to and from the operating circuit and the circuit for direct circulation, as desired. The first connecting line can also be a part of the main lubricant line. A second connecting line is also provided, which connects the direct circulation to the lubricant supply system, and is also connected to the filling line, in conjunction with which the connection is effected after the means for providing or interrupting the flow of operating fluid in the filling line and for the connection and/or disconnection of the filling line, as desired, to and from the operating circuit and the circuit for the circulation of the operating fluid. The connection of the second connecting line is effected to the first connecting line in the direction of flow of the operating fluid after the first nonreturn valve. Also provided in the second connecting line is a valve device, which blocks the flow in one direction, preferably in the form of a so-called nonreturn valve. The two nonreturn valves—the first nonreturn valve and the second nonreturn valve—are executed in this case in such a way that only the directions of flow in the direction of the junction point, i.e. the connection of the second connecting line to the first connecting line, are permitted. This solution ensures that, in the event of the disconnection of the filling line from the operating circuit and the direct circulation, for example in the case of the emptying process or also the conveyance of operating fluid from the toroidal working area in the direct circulation and back to the toroidal working area, the supply to the individual bearing elements is maintained via the lubricant system from the part of the operating fluid that is conveyed outside the toroidal working area, i.e. the direct circulation. The lubricant supply system is thus a part of the operating fluid system. The operating fluid is fed for this purpose via the second connecting line into the first connecting line and is unable to flow back in the direction of the source of the operating fluid thanks to the arrangement of the nonreturn valve, but is forced to flow to the individual bearing elements. The possibility also exists in this case for the provision in the filling line that is disconnected from the direct circulation of a feed device which in addition feeds more operating fluid into the lubricant supply system, in conjunction with which feeding takes place via the first connecting line. This is not absolutely essential, however, and it is accordingly possible to dispense with the actuation of the filling pump or the operating fluid circulation pump in this case, in particular in the event of feeding from an operating fluid tank, which is arranged in a position in which it affected by gravity above the actual bearing elements that are to be supplied. In the other case, i.e. in the event of the connection of the filling line to the circuit for direct circulation, and thus the operating circuit, a part of the operating fluid supplied via the filling line for the lubrication of the bearing elements is diverted via the first connecting line for the lubricant supply system, in conjunction with which this first occurs at a time when the pressure in the circuit for the direct circulation is equal to or greater than the pressure at the feed device.
In a further aspect of the invention, in the solution in accordance with the first proposed solution, means for cleaning the operating fluid, for example in the form of filter devices, are provided in the first connecting line. The filter device in this case is positioned in such a way that it is arranged after the connection of the second connecting line.
In accordance with an additional, second proposed solution, the means for providing the supply to the lubricant supply system in the event of disconnection of the filling line from the direct circulation are formed by a pressure-limiting device and a valve device, which blocks the flow in one direction. The pressure-limiting valve is remotely controlled in this case. One advantage is associated with the ability to dispense with an additional oil filter with a pressure switch to ensure the reliability of the operating mode. The possibility of switching off the feed device also exists. The pressure level itself is scarcely higher than in comparison with the embodiment in accordance with the prior art.
The solutions in accordance with the first and second proposed solutions utilize parts of the filling line, in particular between the means for providing or interrupting the flow of operating fluid to the working area, as a rule a valve device, and the connection of the filling line to the direct circulation for the purpose of taking operating fluid from the direct circulation. The expression “filling line” is understood to denote the line which extends from the source of operating fluid to the direct circulation. No part of the filling line is used, on the other hand, in an execution in accordance with the third proposed solution for the purpose of taking fluid from the direct circulation. A separate connecting line is provided for this purpose between the main lubricant line and the direct circulation. The first connecting line is provided in a similar fashion to the two aforementioned proposed solutions. There is no permanent connection in this case, however, and both the first and the second connecting lines are capable of being connected to the main lubricant line. The means used for ensuring the removal of operating fluid from the circuit for direct circulation for the purpose of lubricating bearing elements by feeding into the lubricant supply system is a valve device controlled by means of control pressure. This is arranged between the two connecting lines and the main lubricant line and is preferably executed as a 3/2-way valve. The lubricant supply system again comprises at least one main lubricant supply line, which is capable of connection to the filling line at least indirectly, and preferably directly, however, and is connected to the bearing elements to be lubricated via additional lines. The connection of these via the first connecting line is effected in the direction of flow from the operating fluid source to the toroidal working area ahead of the means for providing or interrupting the flow of operating fluid in the filling line and for the connection and disconnection of the filling line to and from the circuit for the circulation of the operating fluid and with it the filling line to the working area. In the filled state, the valve device of the means for assuring the removal of operating fluid from the circuit for direct circulation is in a switching position which provides a connection between the operating fluid source and the direct circulation. The means for connection and disconnection are also in a switching position which permits connection of the filling line to the direct circulation. The means for connecting or disconnecting the emptying line to or from the direct circulation in this mode interrupt the flow of operating fluid from the direct circulation to the operating fluid source. The filling process in this mode takes place above all via the connecting line between the direct circulation and the filling line. This means that, for as long as the pressure that is present in the direct circulation is lower than the pressure level in the filling pump, no lubricant will be supplied to the lubricant supply system and the operating fluid in its entirety, including the part intended for the lubricant system, will be conveyed to the coupling as a matter of priority. Not until pressure equilibrium has been reached will the lubricant system also receive a supply. This procedure permits filling of the coupling and readiness for service to be achieved rapidly. With the circulation cooling in its functional mode, the connection between the direct circulation and the operating fluid source is also cleared via the emptying line. Here, too, the provision of the operating fluid is effected essentially via the filling line. In the direct circulation mode, both the filling line and the emptying line, and with them the hydrodynamic coupling, are disconnected from the direct circulation. This means that both valve devices in the filling line are brought into the switching position, in which the flow in the filling line is disconnected from the operating fluid source. In this case, the lubricant supply system is also disconnected from the operating fluid source. Selection of the means for assuring the diversion of operating fluid from the direct circulation preferably takes place in this case depending on the prevailing pressure conditions in the direct circulation. The same advantages as in the other two proposed solutions are also derived from this solution.
In all the solutions, furthermore, additional devices can also be arranged in the circuits, for example cooling devices. These are preferably arranged in the direct circulation. In all the solutions, in addition, the sequence preferably proceeds from the lubricant system into the body of the coupling, so that this quantity of operating fluid is capable of being supplied to the direct circulation via feed devices and a dynamic pressure pump. It is possible to provide circulation lubrication in this way.